[BUG] lua 5.2 luai_hashnum bug with threads

[Andrei <mrpuzzler@...>]

__control87_2 returns the previous state and that Lua could control the FPU precision such that the hash function can
 satisfy the deterministic condition.  Or simply update the comments that 'hash' is quasi-deterministic whereas there are 
certain conditions that lua doesn't check for that could cause the hash function to not operate properly and cause the 
program to not operate as intended and if you want a deterministic function, please roll back to Lua 5.1


Also, although DX is a leading factor, and multiple threads another, it is entirely possible for the LuaVM to be setup under 
one precision, the program change the precision and then the lua state not work, one thread, no DX or threads involved.


Personally, I think that anyone would know better than use floats or doubles as deterministic values, especially anyone 
who has compared two float values without using EPSILON.